This application is a national stage of PCT International Application No. PCT/EP2009/000533, filed Jan. 28, 2009, which claims priority under 35 U.S.C. §119 to German Patent Application No. 10 2008 007 091.2, filed Jan. 31, 2008, the entire disclosure of which is herein expressly incorporated by reference.
The present invention relates to a pre-assembled camshaft module of the general type disclosed in German patent document DE 201 20 912 UI. In this known camshaft module a cylinder head cover is provided which has first bearing halves connected thereto as one piece for the camshaft bearings of a camshaft. In order to produce a pre-assembled camshaft module which can subsequently be screwed to the cylinder head, the camshafts are inserted into the first bearing halves which are integrally formed with the cylinder head cover and the second bearing halves are screwed on. In this way the individual components, cylinder head cover, camshaft and second bearing halves, are pre-assembled to form a module. This pre-assembled camshaft module or cylinder head cover module can then be mounted as a whole on the cylinder head.
A disadvantage of this known camshaft module is that the first bearing halves receiving the camshafts are integrally formed with the cylinder head cover. This means that the cylinder head cover cannot be formed, for example, from synthetic material but must consist of a material which is suitable for the bearing halves for mounting the camshaft and has sufficient strength. The cylinder head cover in accordance with German patent document DE 201 20 912 UI will thus consist of a suitable metal such as aluminum.
It is also disadvantageous that the bearing halves integrally formed with the cylinder head cover have to be worked by a complicated machining process in order to achieve the dimensions, tolerances and surface quality required for mounting the camshaft.
Furthermore, the process of pre-assembling the camshaft module and screwing it to the cylinder head of the internal combustion engine is comparatively complicated in the case of the camshaft module in German patent document DE 201 20 912 UI. Since the second bearing halves are screwed to the first bearing halves integrally formed with the cylinder head cover, the camshaft module pre-assembled in this way must be screwed to the cylinder head at separate attachment points, by separate screws. Two sets of attachment screws and two successive separate screwing processes are required, namely on the one hand the screwing process by which the second bearing halves are screwed to the first bearing halves, and on the other hand the screwing process by which the pre-assembled camshaft module is screwed to the cylinder head.